The urbanised peat-rich coastal-deltaic plain of the Netherlands is severely subsiding due to human-induced phreatic groundwater level lowering, as this causes peat layers to compress and oxidise. To determine the potential susceptibility of this area to future subsidence by peat compression and oxidation, the effects of lowering present-day phreatic groundwater levels were quantitatively evaluated using a subsidence model. Input were a 3D geological subsurface voxel-model, modelled phreatic groundwater levels, and functions for peat compression and oxidation. Phreatic groundwater levels were lowered by 0.25 and 0.5m, and the resulting peat compression and oxidation over periods of 15 and 30 years were determined. The model area comprised the major cities Amsterdam and Rotterdam, and their surrounding agricultural lands.

The results revealed that for these scenarios agricultural areas may subside between 0.3 and 0.8m; potential subsidence in Amsterdam and Rotterdam is considerably lower, less than 0.4m. This is due to the presence of several metres thick anthropogenic brought-up soils overlying the peat below the urban areas, which has already compressed the peat to a depth below groundwater level, and thus minimises further compression and oxidation. In agricultural areas peat is often situated near the surface, and is therefore highly compressible and prone to oxidation. The averaged subsidence rates for the scenarios range between 7 and 13mma−1, which is corresponds to present-day rates of subsidence in the peat areas of the Netherlands. These results contrast with the trend of coastal-deltaic subsidence in other deltas, with cities subsiding faster than agricultural areas. This difference is explained by the driver of subsidence: in other deltas, subsidence of urban areas is mainly due to deep aquifer extraction, whereas in the Netherlands subsidence is due to phreatic groundwater level lowering.

My first year as Editor-in-Chief of the Netherlands Journal of Geosciences / Geologie en Mijnbouw turned out to be a steep learning curve which showed me all the facets this task brings. It has been a productive year, though. A total of 49 papers were published in three regular and two special issues. The special issues, on the Meuse Valley and on Seismicity of the Groningen Gas Field, were well received and contain papers authored by members of academic and applied institutions, including universities, consultants, advisory institutions, provinces, energy operators and regulatory authorities. This once again proves that thematic issues are a great strength of the Journal and it is good to notice that the Journal has become a medium for a broad geoscientific research community.

The Wadden Sea region spans a distance of nearly 500km along the North Sea coast from the Netherlands to Denmark. It consists of a chain of barrier islands which shelter an area of extensive intertidal flats and salt marshes that are dissected by tidal channels and creeks. Moreover, several estuaries are part of this area which is known for its intriguing morphodynamics. The natural process of continuous erosion, transport and deposition of sediment shapes the morphology of the area, which has a high ecological value, especially the intertidal morphology that supports a wide range of wildlife.

The present paper, dedicated to the legacy of local geologist–engineer Peter Jozef (Sjeuf) Felder, who died in 2009, confirms his view that bioclasts constitute a valuable tool in the correlation of outcrops and borehole cores across the type area of the Maastrichtian Stage in the vicinity of Maastricht. His approach of interpreting changes in bioclast contents as having been influenced by Milankovitch cyclicity has here been applied successfully to the entire sedimentary complex of Maastrichtian (latest Cretaceous) age in the study area. In the present approach, results are corroborated by index fossils, mainly dinoflagellate cysts but also calcareous nannofossils, which allow correlation with the Stevns-1 core reference section in eastern Denmark. With the exception of local remnants of Belemnella obtusa Zone age, the Maastrichtian Stage in its type area encompasses the last 4.6 Ma of the Cretaceous Period (i.e. the Belemnella sumensis/Acanthoscaphites tridens Zone up to the K/Pg boundary). P.J. Felder's bioclast analyses have enabled the detection of twelve 400 kyr eccentricity cycles of Milankovitch cyclicity in the area. However, the section is not continuous; there is a hiatus of c.700 kyr between the Gulpen and Maastricht formations at the ENCI-HeidelbergCement Group quarry. In addition, smaller hiatuses, usually in the range of several 20 kyr cycles, have been detected in the upper Maastricht Formation.

The lithostratigraphy, age and human occupation of the Late Glacial and Holocene aeolian succession of a Late Palaeolithic Ahrensburg site in the excavation Geldrop-A2 (municipality of Heeze-Leende) have been investigated. The exposure revealed a stacked sequence of aeolian sand units and intercalated soils (Older Coversand II, Younger Coversand I (YCI), Usselo Soil, Younger Coversand II (YCII), Holocene podzol, drift sand). Fourteen optically stimulated luminescence dates on quartz and three radiocarbon dates provide the age control of the aeolian deposition (coversands, drift sand), landscape stability (soils) and human occupation. The upper part of the YCI unit was dated to the early Late Glacial. The well-developed Usselo Soil was formed during a phase of landscape stability during the late Allerød interstadial and onset of the Younger Dryas stadial. During the Younger Dryas, low aeolian dunes were formed locally (YCII), as a response to landscape instability due to cooling and vegetation decline. In the fine-grained lower part of the YCII unit an initial soil testifies to a decadal to centennial period of landscape stability. An Ahrensburg site in the upper part of this initial soil was dated at 10,915±35 BP (c. 12,854–12,789 cal BP). The lithostratigraphic position, radiocarbon dates of the underlying Usselo Soil and a possibly old-wood effect of up to 200 years suggest that Ahrensburg occupation of the dune environment occurred during the early Younger Dryas, shortly after c. 10,750 BP (12,750 cal BP). Landscape stability and podzol soil formation dominated the early and middle Holocene periods. Drift-sand deposition, probably related to human land use and vegetation decline, occurred in a 200-year period from the 16th to the 18th centuries.

Climate change is very likely to cause a global acceleration in sea-level rise (SLR). The projected acceleration of SLR will also affect the Wadden Sea. In addition to an accelerated SLR, gas and salt extraction will cause subsidence that adds to an increase in water depth in the tidal basins. This will have consequences for the sediment budget of the Wadden Sea and especially for the intertidal flats that have a high ecological value. This synthesis presents projections of the future state of the Dutch Wadden Sea for the years 2030, 2050 and 2100.

The projected changes in mean sea level by 2100 for Den Helder and Delfzijl are above the global mean projections, mainly due to the above-average ocean dynamics and glacio-isostatic adjustment contributions in the regional projections. The projected rise in mean sea level for 2100 with relation to 2018 in these locations is 0.41m, 0.52m and 0.76m for, respectively, the RCP2.6, RCP 4.5 and RCP8.5 climate scenarios.

When we combine the presented SLR scenarios with the subsidence estimates and compare these rates to the critical rates for ‘drowning’ of intertidal flats that were calculated for the individual tidal basins, we can determine the moment that the maximum imported sediment volume can no longer compensate the increase in accommodation space in a basin and the intertidal flats will start to diminish in surface area and/or height. In the RCP2.6 scenario, the projected rates of relative SLR will be below the critical rate for drowning of the inlet systems in the Dutch Wadden Sea. For the RCP4.5 scenario, the critical SLR rate will be exceeded for Vlie Inlet in 2030, and for the RCP8.5 scenario the critical SLR rate will be exceeded for Vlie Inlet in 2030, Texel Inlet in 2050 and Ameland Inlet in 2100. For the other basins the critical rate will not be exceeded until 2100 or later.

The way the intertidal flats in a basin will react to ‘drowning’ is not clear beforehand. It is highly possible that erosion of flats in one place will produce the sediment to maintain flats in other places. Tidal flats close to the sediment-delivering tidal inlet are not likely to disappear, because there the balance between supply and erosion is not likely to change.

Rising sea levels due to climate change can have severe consequences for coastal populations and ecosystems all around the world. Understanding and projecting sea-level rise is especially important for low-lying countries such as the Netherlands. It is of specific interest for vulnerable ecological and morphodynamic regions, such as the Wadden Sea UNESCO World Heritage region.

Here we provide an overview of sea-level projections for the 21st century for the Wadden Sea region and a condensed review of the scientific data, understanding and uncertainties underpinning the projections. The sea-level projections are formulated in the framework of the geological history of the Wadden Sea region and are based on the regional sea-level projections published in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5). These IPCC AR5 projections are compared against updates derived from more recent literature and evaluated for the Wadden Sea region. The projections are further put into perspective by including interannual variability based on long-term tide-gauge records from observing stations at Den Helder and Delfzijl.

We consider three climate scenarios, following the Representative Concentration Pathways (RCPs), as defined in IPCC AR5: the RCP2.6 scenario assumes that greenhouse gas (GHG) emissions decline after 2020; the RCP4.5 scenario assumes that GHG emissions peak at 2040 and decline thereafter; and the RCP8.5 scenario represents a continued rise of GHG emissions throughout the 21st century. For RCP8.5, we also evaluate several scenarios from recent literature where the mass loss in Antarctica accelerates at rates exceeding those presented in IPCC AR5.

For the Dutch Wadden Sea, the IPCC AR5-based projected sea-level rise is 0.07±0.06m for the RCP4.5 scenario for the period 2018–30 (uncertainties representing 5–95%), with the RCP2.6 and RCP8.5 scenarios projecting 0.01m less and more, respectively. The projected rates of sea-level change in 2030 range between 2.6mma−1 for the 5th percentile of the RCP2.6 scenario to 9.1mma−1 for the 95th percentile of the RCP8.5 scenario. For the period 2018–50, the differences between the scenarios increase, with projected changes of 0.16±0.12m for RCP2.6, 0.19±0.11m for RCP4.5 and 0.23±0.12m for RCP8.5. The accompanying rates of change range between 2.3 and 12.4mma−1 in 2050. The differences between the scenarios amplify for the 2018–2100 period, with projected total changes of 0.41±0.25m for RCP2.6, 0.52±0.27m for RCP4.5 and 0.76±0.36m for RCP8.5. The projections for the RCP8.5 scenario are larger than the high-end projections presented in the 2008 Delta Commission Report (0.74m for 1990–2100) when the differences in time period are considered. The sea-level change rates range from 2.2 to 18.3mma−1 for the year 2100.

We also assess the effect of accelerated ice mass loss on the sea-level projections under the RCP8.5 scenario, as recent literature suggests that there may be a larger contribution from Antarctica than presented in IPCC AR5 (potentially exceeding 1m in 2100). Changes in episodic extreme events, such as storm surges, and periodic (tidal) contributions on (sub-)daily timescales, have not been included in these sea-level projections. However, the potential impacts of these processes on sea-level change rates have been assessed in the report.

Due to canal-digging activities in 2011 and 2014, two small and one large temporary exposure, all ranging from 4 to 5 m in depth, were studied with respect to the sedimentology and structural geology, in the glacial ridge of Midwolda, Groningen, the Netherlands. The lowermost unit consists of clay of Elsterian age and is composed of glaciolacustrine and turbiditic deposits (Peelo Formation). These show synsedimentary deformations due to loading, as well as post-sedimentary Saalian glaciotectonic deformations, consisting of folding, and faulting structures. The overlying Saalian till sequence consists of two main units. The lower unit, with clear features of a subglacial deformation zone (e.g. lateral heterogeneity), has a local origin and strongly resembles the underlying Elsterian clay. Glacial tectonic and morphological observations indicate a primary NE–SW ice-flow direction. The second till layer has a sandy texture and high crystalline gravel content, while glacial-tectonic indicators point to a NW–SE ice-flow direction. The deformation of the till layers has caused a repetition and mixing of till layers, due to the last ice movement. The NW–SE ice movement is supported by the morphology as well as data from erratic gravel counts. Correlation with geological cross-sections strongly suggests regional subsurface control on ice-sheet behaviour.

This paper presents new geological data from two terp excavations at Englum and Ezinge, in the Dutch province of Groningen, and compares them to similar data from the western part of Friesland, in particular from the terp of Wijnaldum-Tjitsma. This terp is situated at a salt marsh ridge of the same height and thickness as Englum and Ezinge, although habitation started 650 years later at Wijnaldum. The measured levels of the tidal-flat/salt-marsh boundary underneath these terps make it possible to reconstruct palaeo-Mean High Water (MHW) levels. These sea-level index points show that palaeo-MHW in the Groningen part of the Wadden Sea was at the upper limit of the range of palaeo-MHW that has been reconstructed for the Dutch Wadden Sea on the basis of data from its western part. The deviating levels indicate that there are differences between regions of the Wadden Sea; this has earlier been established for the German section of the Wadden Sea. In the eastern part of the Dutch Wadden Sea, MHW nowadays is considerably higher than in the western part of the Wadden Sea; the data suggest that this may have been the case already in the 1st millennium BC. Salt marsh levels under dated terp layers make it possible to establish the rate of sedimentation of the developing salt marsh, at 23–91 cm per century for the pioneer zone and low marsh. This rate of development slowed to 4–5 cm per century for the middle marsh and 3–4 cm per century for the high salt marsh.

In this study we apply an evidence-based approach to model population-size fluctuations and their corresponding impact on land use during the Roman and early-medieval periods in the Rhine–Meuse delta in the present-day Netherlands. Past-population numbers are reconstructed based on Roman and early-medieval settlement patterns. Corresponding impacts of these demographic fluctuations on potential land use are calculated by integrating the newly developed demographic overviews with archaeological and geoscientific data using a new land-use model termed ‘Past Land-Use Scanner’ (PLUS). The primary aims are to reconstruct first-millennium palaeodemographics and to explore the potential of simulation modelling for testing the feasibility of archaeological hypotheses regarding past land use. Results show that in the study area the first millennium AD was characterised by two periods during which major population growth occurred: the middle-Roman period (AD 70–270) and early-medieval period C (AD 725–950). A major demographic decline of 78–85% occurred during the late-Roman period (AD 270–450), after which first-millennium population numbers never again reached middle-Roman period levels. The modelling outcomes demonstrate that the impact of population fluctuations (growth vs decline) on the limits of the natural landscape during the first millennium in general was low. During these thousand years, the natural landscape almost without exception (only scenario D deviates) provided sufficient options for arable farming, meadows and pastures and was not a limiting factor for population growth. These results underline the added value of simulation modelling for testing the feasibility of archaeological hypotheses and analysing human–landscape interactions in the past.

Ground surface dynamics is one of the processes influencing the future of the Wadden Sea area. Vertical land movement, both subsidence and heave, is a direct contributor to changes in the relative sea level. It is defined as the change of height of the Earth's surface with respect to a vertical datum. In the Netherlands, the Normaal Amsterdams Peil (NAP) is the official height datum, but its realisation via reference benchmarks is not time-dependent. Consequently, NAP benchmarks are not optimal for monitoring physical processes such as land subsidence. However, surface subsidence can be regarded as a differential signal: the vertical motion of one location relative to the vertical motion of another location. In this case, the actual geodetic height datum is superfluous.

In the present paper, we highlight the processes that cause subsidence, with specific focus on the Wadden Sea area. The focus will be toward anthropogenic causes of subsidence, and how to understand them; how to measure and monitor and use these measurements for better characterisation and forecasting; with some details on the activities in the Wadden Sea that are relevant in this respect. This naturally leads to the identification of knowledge gaps and to the formulation of notions for future research.

The Wadden Sea is a unique coastal wetland containing an uninterrupted stretch of tidal flats that span a distance of nearly 500km along the North Sea coast from the Netherlands to Denmark. The development of this system is under pressure of climate change and especially the associated acceleration in sea-level rise (SLR). Sustainable management of the system to ensure safety against flooding of the hinterland, to protect the environmental value and to optimise the economic activities in the area requires predictions of the future morphological development.

The Dutch Wadden Sea has been accreting by importing sediment from the ebb-tidal deltas and the North Sea coasts of the barrier islands. The average accretion rate since 1926 has been higher than that of the local relative SLR. The large sediment imports are predominantly caused by the damming of the Zuiderzee and Lauwerszee rather than due to response to this rise in sea level. The intertidal flats in all tidal basins increased in height to compensate for SLR.

The barrier islands, the ebb-tidal deltas and the tidal basins that comprise tidal channels and flats together form a sediment-sharing system. The residual sediment transport between a tidal basin and its ebb-tidal delta through the tidal inlet is influenced by different processes and mechanisms. In the Dutch Wadden Sea, residual flow, tidal asymmetry and dispersion are dominant. The interaction between tidal channels and tidal flats is governed by both tides and waves. The height of the tidal flats is the result of the balance between sand supply by the tide and resuspension by waves.

At present, long-term modelling for evaluating the effects of accelerated SLR mainly relies on aggregated models. These models are used to evaluate the maximum rates of sediment import into the tidal basins in the Dutch Wadden Sea. These maximum rates are compared to the combined scenarios of SLR and extraction-induced subsidence, in order to explore the future state of the Dutch Wadden Sea.

For the near future, up to 2030, the effect of accelerated SLR will be limited and hardly noticeable. Over the long term, by the year 2100, the effect depends on the SLR scenarios. According to the low-end scenario, there will be hardly any effect due to SLR until 2100, whereas according to the high-end scenario the effect will be noticeable already in 2050.